Catheters which are used to remove occlusive material from lumens within the body are well known. Occlusive material such as plaque, atheroma, and emboli vary in their mechanical properties and various energy sources have been proposed to break up occlusive material. These proposals include the use of high energy fluid jets or the circulation of an abrasive slurry within the vessel. The use of mechanical impellers and/or blades has been proposed and experimental work has been performed with a "rotoblader" device. Laser light energy and either ultrasonic or acoustic energy have been proposed to breakdown occlusive material. The use of radio frequency electromagnetic energy has been proposed as well. For example fluid pressure thrombectomy systems are known from U.S. Pat. No. 4,690,672 to Veltrup among others. In the Veltrup device, a reward-facing jet entrains thrombus and blood from the patient, and ejects these into a secondary discharge lumen which removes both thrombus and blood from the body. Linear or straight line fluid jets which represent the current technology, are relatively inefficient in removing thrombus because of the jet geometry.
Impeller based cutting devices are known from U.S. Pat. No. 4,729,763 among others. In this device the mechanically rotated blade interacts directly with the occlusive material.
Ultrasonic based devices are known from U.S. Pat. No. 5,368,557. In this device the ultrasonic energy is used to break up the occlusive material and a fluid is supplied to cool the ultrasonic tip. In general there are two functions which must be supplied. First sufficient energy must be available to disrupt the occlusive material. Secondly loose material must be efficiently removed from the body. Most particulate occlusive material is thrombogenic and failure to remove this material can result in a distal embolism.